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Archive for June, 2015
Posted by Jack Crossfire | Jun 28, 2015 @ 05:13 PM | 4,842 Views
After waking up expecting to see another rocket barely miss a barge or delayed launch, was surprised to see it exploded during liftoff. Of the 3 camera angles, the best one came from NASA TV, then was rereleased with banner ads & annotations.

Falcon 9 explosion from 3 cameras (1 min 13 sec)


The 2nd stage oxygen tank was the scene of many launch delays. Stuck valves, leaky pipes abounded. Not surprising that it finally blew up, probably from a stuck valve.

It's now been 2 consecutive failures in reaching the space station. The last successful mission was April 14. The Soyuz on April 28 failed. The last Cygnus attempt failed on Oct 28, 2014. Only 4 of the last 7 missions made it. The chance of reaching Mars has been better than reaching the space station.

The increasing rate of failures as rocket companies reach ever higher valuations makes you wonder when something has to work to be worth $10 billion & when it just has to be worth $10 billion to prevent a recession.
Posted by Jack Crossfire | Jun 20, 2015 @ 05:45 PM | 4,488 Views




NASA's last space shuttle external tank to complete Endeavour L.A. exhibit

Another win for Calif*. Now only the boosters will be fake, if the exhibit is ever funded. Completion was once envisioned in 2015, then it was 2018, but it was always based on donations & refinancing. If ever delivered, it'll be another spectacle as its transported down the streets of LA. Too bad some water can't be delivered in the tank.


Nearly a year after its inception, the travel fan has been highly successful at defeating the heat. It hasn't chopped any limbs off, hasn't tipped over. Keeping it close & blocking off the area around it has kept kids away from it. Humans are strangely attracted to putting their hands in spinning blades, especially Americans. Limiting the power to 1/4 power has left enough airflow on 12V.

On the downside, it became clear Chinese RC motors aren't capable of running continuously for days. It wasn't long before its RPM fluctuated, then it sometimes stalled & clicked. The bearings failed. Frequent lubrication has kept the bad bearings going.

Also, it's still noisy, despite every effort to silence PWM noise. The commutation noise & shaft resonance are deafening at low RPMs.

The 15 year old squirrel cage blower would make a comeback if not for the fact that it needs to be hosed down with a high pressure nozzle & the outdoor water was shut off.
Posted by Jack Crossfire | Jun 19, 2015 @ 11:33 PM | 4,750 Views
Posted by Jack Crossfire | Jun 18, 2015 @ 01:40 AM | 4,752 Views
Finished it in 32 miles of pounding up & down the trail. The title alone conjured the imagination. Long ago, Carl Segan said one day we would find life on Mars & the martians would be us. The title was obviously a play on that nugget.

It definitely has a few flaws. The mathematical descriptions sometimes get tedious, yet some of his solutions to problems are over simplified & wouldn't really work. It's technical sounding enough to sound like everything is factual. Sounding accurate is what it does better than any other book.

Otherwise, it works. It's easy enough to see how the general direction in the hacking of the various parts could work in real life. It's interesting to see how many different ways the oxygenator & water reclaimer could be basterdized to do virtually any task & to imagine a world where NASA produced stuff that really did work. If the movie is done right, it could invigorate a lot of interest in funding a space program, for a time. A book isn't accessible enough to reach enough people, but a movie might.

There were many attempts to make a movie about traveling to Mars. None got it right, showing how hard the task was. This one might get it right.





In other news, Fitbit finally had their IPO, but more importantly in today's terms, was valued at $4 billion. In creating unlimited free credit, Old Yellen solved the problem of monetizing private data that companies had no right to sell. They would just sell...Continue Reading
Posted by Jack Crossfire | Jun 14, 2015 @ 10:46 PM | 5,364 Views


The decision was finally made to retire the 4 original, low efficiency monocopters & the world's greatest battery charger to the landfill.

...Continue Reading
Posted by Jack Crossfire | Jun 13, 2015 @ 01:57 AM | 4,343 Views
Realtime running form feedback

There was the vaporware http://www.runscribe.com/, which claimed to capture running form for viewing at a later time. Fitbit & all the other uprated pedometers captured step rate for viewing at a later time. The trick is none ever provided realtime feedback. They were all intended to gather data for the company to sell to advertizers, not focused on providing any realtime feedback to the user.

A metronome is very good at providing realtime stimulus for step rate. The same thing hasn't been achieved for kinematics. Step 1 is capturing the body positions. Maybe accelerometers or autonomous drones could do it.

Step 2 is stimulating the athlete to adjust positions. A key stimulus would be moving a leg vertically or leaning at the right angle. Maybe pager motors could be strapped to the limbs. Nowadays, they're called "haptics" & worth many billions of dollars. To a child of the 80's, they will always be pager motors. There are also ways of creating brief pushing & pulling forces, by moving weights. Actuators for training body movements could be too heavy.

A kinematic simulating device would allow you to feel how a famous athlete poses. Famous performances could be recorded & played back through the pose stimulators. Reproducing a dance move with subtle pushing forces from actuators might be extremely slow & tedious, but something repetitive like running might be more practical.
Posted by Jack Crossfire | Jun 10, 2015 @ 12:20 AM | 5,256 Views
Posted by Jack Crossfire | Jun 08, 2015 @ 11:44 PM | 4,855 Views






So after running to the Apple store & waiting 30 minutes for a guy to finish with the 5k monitor, it became quite clear that I didn't have enough money to develop a 4k user interface. Had created a mockup to test out asset sizes, based on downloadable screenshots. It was too small on the 5k monitor. The screenshots were for a completely different monitor that the author had no idea of the resolution of.

The original plan was to make assets double the size of a 2.5k monitor, but the downloadable screenshots showed them using 1.5x the size. In the end, 2x size was probably right. Also, instead of making a fully functional interface, it would be best to just mock up a screen with the desired sizes. It's still completely impractical to design a user interface by loading mockups in an Apple store.

The standard resolution of the next generation of monitors will probably be 5k instead of 4k, just as it was previously 2.5k instead of 2k. The extra pixels allow a complete video frame to fit in a user interface. It makes sense when going from 2.5k to 5k to double the asset sizes. It's also much easier than making them 1.5x. It may be necessary to have double size assets for 5k & 1.5x size assets for 4k.

Unfortunately, I grew up in a time when the best monitors consumers could get were $200. Now, the crappiest 4k monitors are $400. The 5k Apple monitor has a $1900 tag & requires also paying for the embedded computer. Paychecks are getting smaller & rent is going up by amounts that would pay for a new 5k monitor every month. It's 1 of those times you realize the limits of mortality. Mortals can't save money or have everything.
Posted by Jack Crossfire | Jun 07, 2015 @ 01:52 AM | 4,785 Views






After much debate, finally built it. The RC fan shroud was noisy & reduced airflow. A screen which allowed air through might do better than cardboard. The motor is still too noisy, so the debate is on about reverting to the larger motor.
Posted by Jack Crossfire | May 31, 2015 @ 09:00 PM | 5,898 Views
Solar powered rover photovore thing:

These were popular, 10 years ago. They have no purpose besides reusing parts. There are some giant electrolytic caps & solar panels are slightly cheaper than the old days. The mane problem is all wheeled vehicles get stuck. There was a ramp up in photovore videos when they were popular, then nothing more to do with them was found.


Bluetooth sliding door lock:

The mechanics are simple, but the encryption is hard. Keyless entry systems have been around forever, but are actually an interesting problem. You can't just send a fixed packet to unlock them. The receiver & transmitter contain a pseudo random number generator which is synchronized. Every unlock command uses a different code from the random number generator. If an unlock command is missed, the receiver tests a certain number of future codes. The receiver can only miss a certain number of commands before it requires resynchronization.